Reference pictures are widely used by video encoders and decoders (e.g., MPEG2, H.264, and H.265) for motion estimation (ME) and motion compensation (MC) to reduce inter-frame redundancy. In network-based (e.g., Internet-based) video transmission, an encoded bitstream including reference pictures can be transmitted, using packets as transmission units, over a network to a receiving decoder. When jamming occurs in the network, a packet can be lost during transmission or delayed at the decoder (which is deemed as lost). Packet loss can cause loss of a whole or a part of the picture, such as a slice. When the lost packet includes information to be used as part of a reference picture, the decoding process will suffer because future pictures rely on the lost information for decoding.
One type of reference pictures, the I-picture, is prone to packet loss. I-pictures typically need more bits (e.g., multiple times that needed by P-pictures) to encode. In addition, I-pictures need more packets and bandwidth to transmit and typically cause a network burst.
To alleviate difficulties caused by a network jam, one solution is to resend the lost packets of a key picture (e.g., an I-picture). However, resending the lost packets causes additional network traffic, which could further aggravate the network jam.